1. Field of the Invention
The present invention relates to a lyophobic treatment method, a nozzle plate, an inkjet head and an electronic device, and more particularly, to technology for lyophobic treatment of a surface of a base material having a hole section.
2. Description of the Related Art
In a recording head used in an inkjet recording apparatus (an inkjet head), if ink adheres to the surface of the nozzle plate (in particular, to the periphery of the nozzle openings), then the ink droplets ejected from the nozzles are thereby affected, giving rise to variation in the ejection direction of the ink droplets and making it difficult to deposit the ink droplets at the prescribed positions on the recording medium, and therefore giving rise to decline in image quality.
Therefore, in order to prevent ink from adhering to the surface of the nozzle plate, various methods have been proposed for forming a lyophobic film on the surface of a nozzle plate (also called “nozzle forming substrate” hereinafter).
Japanese Patent Application Publication No. 2007-261070 describes a method according to which a lyophobic film is formed on the surface (ink ejection surface) of a nozzle forming substrate having nozzle holes and on the inner wall faces of the nozzles, whereupon a protective tape (masking tape) is attached to the lyophobic film formed on the surface of the nozzle forming substrate, a plasma process is applied from the rear surface side of the nozzle forming substrate (the side opposite to the ink ejection surface) with this protective tape in an attached state, thereby removing the lyophobic film on the inner wall faces of the nozzles, and the protective tape is then detached from the nozzle forming substrate. In this way, the surface of the nozzle forming substrate is subjected to lyophobic treatment.
However, in the method described in Japanese Patent Application Publication No. 2007-261070, as shown in FIG. 7A, after forming a lyophobic film 904 on the surface (the upper face in FIGS. 7A and 7B) and the inner wall faces of nozzles of the nozzle forming substrate 900 having nozzle holes 902, a protective tape 906 is attached to the lyophobic film 904 on the surface of the nozzle forming substrate 900 and the lyophobic film 904 on the inner wall faces of the nozzles is removed by carrying out plasma processing from the rear surface side (the lower surface in FIGS. 7A and 7B) of the nozzle forming substrate, but if the removal by plasma processing advances too far, then as shown in FIG. 7B, the lyophobic film 904 is removed excessively up to the peripheral portions of the openings of the nozzle holes 902, and this causes the ink ejection performance and the maintenance characteristics to decline. Furthermore, when the protective tape 906 is bonded onto the lyophobic film 904 on the surface of the nozzle forming substrate 900, the protective tape 906 may not adhere completely to the lyophobic film 904 due to the properties of the lyophobic film 904, and consequently there is also a problem in that non-uniformity is liable to occur in the lyophobic properties. Moreover, in cases such as this, there is a possibility that the excessive removal of the lyophobic film 904 progresses further.